Scientific evidence for minimally invasive total knee arthroplasty

Total knee arthroplasty is often considered one of the most successful surgical operations, with implant survival rates as high as 95% reported over follow-up periods of 15 to 20 years. Despite these excellent reported results, some level of outcome dissatisfaction is reported in a considerable numbers of patients. Minimally invasive surgical techniques have been developed in an attempt to reduce or eliminate the surgical factors perceived to contribute to this dissatisfaction. An overview of minimally invasive total knee arthroplasty, with specific focus on level I (prospective, randomized) studies when available is presented along with an examination of how the published literature supports some of the more commonly stated benefits and drawbacks of minimally invasive techniques. Minimally invasive total knee arthroplasty generally encompasses the following goals: reduced skin incision size, minimal or no incision of the extensor muscles and quadriceps tendon, minimal or no eversion of the patella, the use of downsized instrumentation, making bone cuts in situ, and minimal dislocation of the knee joint. Five principal surgical approaches have been developed that incorporate these aims, and, to date, four level I studies have been reported that compare the results of one or more of these techniques to traditional total knee arthroplasty. Three of these four studies showed no knee score differences at 3 months; one study showed higher scores at up to 9 months follow-up. In the opinion of the authors, these surgeons may have still been on their learning curve. Further studies that examine patients treated by surgeons who have mastered minimally invasive techniques may provide further insight into the true benefits and drawbacks of these techniques.